Three new studies affirm there has been no significant change in natural disasters, precipitation, or bushfire across Australia for the last several decades.
Instances when perilous flooding, droughts, bushfires, cyclones, storms, heatwaves…occur at the nearly same time are classified as “compound disaster” events.
Across Australia, there has been no statistically significant trend in compound disaster events over any period in the last 50 years.
The predominant and most predictable driver of climate-related disaster events is not anthropogenic global warming, or CO2 emissions, but the El Nino Southern Oscillation.
“Here we utilise an Australian natural disaster database of normalised insurance losses to show compound disasters are responsible for the highest seasonal financial losses. Though their component events occur most frequently in the eastern seaboard, they may also comprise disasters on both sides of the continent. There has been no temporal trend in their frequency since 1966. A new compound disaster scale is proposed for Australian conditions. A bootstrapping analysis reveals the pairing of Bushfire and Tropical Cyclone to occur far less often than would be expected by chance. This is because these perils occur most frequently under contrasting climate states. Climate variability influences the frequency, intensity and type of perils contributing to compound disasters with the clearest relationship being with the El Niño Southern Oscillation. Given that ENSO is the most predictable climate driver at seasonal timescales, this may assist better forecasting of their occurrence and higher degrees of readiness.”
Image Source: Gissing et al., 2021
Precipitation patterns across Australia also show no detectable trend in the last 50 years, as some regions have experienced more rainfall and some less rainfall.
As a whole, however, the country has become slightly wetter since 1960 (as indicated by the larger concentrations of blue in the below images).
“Northern parts of Australia have experienced increasing annual rainfall totals, resulting in increased water availability in the tropics with increased soil moisture, evapotranspiration, and runoff, particularly during the hot, wet monsoon season. In contrast, the southwest and southeast coast of Australia have experienced declines in rainfall, particularly in the colder months, corresponding with decreasing evapotranspiration, soil moisture, and runoff. Trends in flooding are aligned with runoff trends, and closely follow trends in rainfall, with changes in soil moisture of secondary influence. Streamflow droughts, measured by the standardised runoff index, are increasing across large parts of Australia, with these increases more widespread than changes in rainfall alone. Increases in rainfall in the tropics of northern Australia appear to be related to decreasing drought occurrence and extent, but this trend is not universal, suggesting changes in rainfall alone are not an indicator of changing drought conditions.”
